Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

A1CAC9

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N2140U · BOEING 777-300ER · operated by UNITED AIRLINES INC

Hex
A1CAC9
Octal
50345311
Decimal
10,603,209
Country
US
Tail
N2140U
Type
B77W
No current signal · last broadcast Jul 26, 21:35 UTC
Flights observed
178
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 21:35 UTC

Last known position

Most recent position reported by Mode-S A1CAC9.

Country allocation

The ICAO 24-bit address A1CAC9 falls within the block assigned to United States (US) by ICAO Annex 10, Volume III. Every aircraft registered in United States receives a permanent address from this block at the time of registration; the address stays with the airframe even if the aircraft is re-registered to a different operator within the country.

Callsign history 20 distinct

Callsign Airline Flights Last seen
UAL858 United Airlines 11 2026-07-18
UAL857 - 11 2026-07-17
UAL989 - 8 2026-07-02
UAL837 - 8 2026-07-21
UAL78 United Airlines 8 2026-07-22
UAL951 United Airlines 7 2026-07-02
UAL950 - 7 2026-07-01
UAL878 - 6 2026-07-14
UAL862 United Airlines 6 2026-07-21
UAL190 - 6 2026-06-28
UAL988 - 5 2026-07-01
UAL877 United Airlines 5 2026-07-20
UAL872 United Airlines 5 2026-07-26
UAL869 - 5 2026-07-13
UAL838 - 5 2026-07-16
UAL79 - 5 2026-07-15
UAL43 - 5 2026-07-03
UAL1960 - 5 2026-07-10
UAL1175 United Airlines 5 2026-07-26
UAL871 United Airlines 4 2026-07-25

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 UAL1175 SFO → HNL Jul 26, 21:15 UTCJul 26, 21:35 UTC20m
2026-07-26 UAL1175 SFO → HNL Jul 26, 16:40 UTCJul 26, 17:10 UTC30m
2026-07-26 UAL872 TPE → SFO Jul 26, 03:50 UTCJul 26, 13:05 UTC9h 16m
2026-07-26 UAL872 TPE → SFO Jul 26, 02:00 UTCJul 26, 02:20 UTC20m
2026-07-25 UAL871 SFO → TPE Jul 25, 10:05 UTCJul 25, 10:15 UTC10m
2026-07-24 UAL871 SFO → TPE Jul 24, 22:23 UTCJul 25, 10:16 UTC11h 53m
2026-07-24 UAL871 SFO → TPE Jul 24, 22:25 UTCJul 25, 08:50 UTC10h 25m
2026-07-23 UAL984 CDG → SFO Jul 23, 07:45 UTCJul 23, 18:50 UTC11h 5m
2026-07-22 UAL57 EWR → CDG Jul 22, 22:59 UTCJul 23, 05:15 UTC6h 16m
2026-07-22 UAL57 EWR → CDG Jul 22, 22:50 UTCJul 23, 05:15 UTC6h 25m
2026-07-22 UAL78 NRT → EWR Jul 22, 12:55 UTCJul 22, 20:00 UTC7h 5m
2026-07-22 UAL78 NRT → EWR Jul 22, 08:51 UTCJul 22, 19:53 UTC11h 2m
2026-07-21 UAL837 SFO → NRT Jul 21, 19:58 UTCJul 22, 05:46 UTC9h 48m
2026-07-21 UAL837 - Jul 21, 20:00 UTCJul 22, 05:25 UTC9h 25m
2026-07-21 UAL862 HKG → SFO Jul 21, 04:30 UTCJul 21, 16:50 UTC12h 20m
2026-07-20 UAL877 SFO → HKG Jul 20, 16:40 UTCJul 20, 20:45 UTC4h 5m
2026-07-20 UAL877 SFO → HKG Jul 20, 07:40 UTCJul 20, 08:05 UTC25m
2026-07-19 UAL810 PHL → DEN Jul 19, 13:50 UTCJul 20, 02:10 UTC12h 20m
2026-07-18 UAL809 SEA → IAD Jul 18, 22:40 UTCJul 19, 11:15 UTC12h 35m
2026-07-18 UAL858 ICN → SFO Jul 18, 05:50 UTCJul 18, 07:30 UTC1h 40m
2026-07-18 UAL858 ICN → SFO Jul 18, 04:44 UTCJul 18, 16:19 UTC11h 35m
2026-07-17 UAL858 ICN → SFO Jul 17, 08:20 UTCJul 18, 07:30 UTC23h 11m
2026-07-17 UAL857 - Jul 17, 07:25 UTCJul 18, 06:15 UTC22h 51m
2026-07-16 UAL857 SFO → PVG Jul 16, 22:27 UTCJul 17, 09:55 UTC11h 28m
2026-07-16 UAL857 - Jul 16, 22:30 UTCJul 16, 23:05 UTC35m
2026-07-16 UAL838 - Jul 16, 08:25 UTCJul 16, 17:45 UTC9h 20m
2026-07-15 UAL79 - Jul 15, 15:55 UTCJul 16, 05:05 UTC13h 10m
2026-07-15 UAL2416 SFO → EWR Jul 15, 07:30 UTCJul 15, 12:15 UTC4h 45m
2026-07-14 UAL878 HKG → SFO Jul 14, 14:55 UTCJul 15, 03:25 UTC12h 29m
2026-07-13 UAL869 SFO → HKG Jul 13, 21:22 UTCJul 14, 10:24 UTC13h 2m
2026-07-13 UAL869 - Jul 13, 21:25 UTCJul 13, 21:50 UTC25m
2026-07-13 UAL838 - Jul 13, 08:35 UTCJul 13, 17:55 UTC9h 20m
2026-07-12 UAL837 SFO → NRT Jul 12, 19:52 UTCJul 13, 05:59 UTC10h 7m
2026-07-12 UAL837 - Jul 12, 19:55 UTCJul 13, 06:05 UTC10h 10m
2026-07-12 UAL858 PVG → SFO Jul 12, 04:44 UTCJul 12, 15:24 UTC10h 40m
2026-07-12 UAL858 PVG → SFO Jul 12, 04:44 UTCJul 12, 15:12 UTC10h 28m
2026-07-11 UAL858 - Jul 11, 08:20 UTCJul 12, 07:01 UTC22h 40m
2026-07-11 UAL857 - Jul 11, 06:55 UTCJul 12, 06:15 UTC23h 20m
2026-07-10 UAL857 SFO → PVG Jul 10, 21:17 UTCJul 11, 09:33 UTC12h 16m
2026-07-10 UAL857 - Jul 10, 21:10 UTCJul 11, 08:15 UTC11h 5m
2026-07-10 UAL1960 - Jul 10, 12:05 UTCJul 10, 17:10 UTC5h 5m
2026-07-10 UAL1960 - Jul 10, 11:40 UTCJul 10, 12:00 UTC20m
2026-07-09 UAL78 - Jul 9, 08:55 UTCJul 9, 21:25 UTC12h 30m
2026-07-09 UAL78 NRT → EWR Jul 9, 08:51 UTCJul 9, 21:18 UTC12h 27m
2026-07-08 UAL837 SFO → NRT Jul 8, 20:00 UTCJul 9, 06:05 UTC10h 5m
2026-07-08 UAL1960 - Jul 8, 11:35 UTCJul 8, 16:50 UTC5h 15m
2026-07-07 UAL78 NRT → EWR Jul 7, 08:40 UTCJul 7, 16:15 UTC7h 35m
2026-07-07 UAL78 NRT → EWR Jul 7, 08:51 UTCJul 7, 20:30 UTC11h 39m
2026-07-06 UAL79 EWR → NRT Jul 6, 16:02 UTCJul 7, 05:14 UTC13h 12m
2026-07-06 UAL79 EWR → NRT Jul 6, 16:20 UTCJul 7, 05:05 UTC12h 45m

About Mode-S

A Mode-S transponder code (also called an "ICAO 24-bit address" or "hex code") is a 6-character hexadecimal identifier permanently assigned to an aircraft when it's first registered. Unlike callsigns (which change with each flight) or registrations (which can change if an aircraft is sold internationally), the Mode-S address stays with the airframe for the life of the aircraft in that country.

Every ADS-B transmission from an aircraft includes its Mode-S address, making it the most reliable way to identify a specific airframe. Flight-tracking services like Apparatus use the Mode-S address as the primary key for tying position broadcasts, callsigns, and ownership records together.

Prefer a tail-number view? See the N2140U page for operator, model, and routing details .

Mode-S A1CAC9 frequently asked

What is Mode-S code A1CAC9?
A1CAC9 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N2140U.
Where is Mode-S A1CAC9 registered?
Mode-S code A1CAC9 is allocated to United States (US). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is A1CAC9 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 21:35 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A1CAC9, octal 50345311, decimal 10,603,209.
What flights does A1CAC9 operate?
Mode-S A1CAC9 has broadcast 20 distinct callsigns, including UAL858, UAL857, UAL989, UAL837, UAL78.